Gliricidia Little Leaf Disease in Costa Rica.

Gliricidia sepium is a multipurpose, legume tree species native to Central America and Mexico with wide social and economic importance. Gliricidia little leaf disease (GLLD) is associated with infection by a phytoplasma and is manifested by one or more symptoms, including leaflet yellowing, leaflet size reduction, shortened internodes, and shoot proliferation, often leading to branch die-back or death of young trees. Trees with symptoms were seen in fences and natural stands in the Nicoya Peninsular and on road sides west of San Jose, Costa Rica. Shoot samples were collected from eight symptom-bearing trees in different locations and from two healthy-looking trees in the southeast where no GLLD symptoms were observed. DNA from each sample was used as template in polymerase chain reaction (PCR) with universal phytoplasma rRNA gene primers P1 and P7 (1). DNA from a GLLD-infected tree from Honduras, and a pigeon pea witches'-broom infected Cajanus cajan from Florida, served as positive controls, while DNA from healthy G. sepium and C. cajan seedlings were used as negative controls. A 1.8-kb PCR product, indicative of presence of phytoplasma DNA, was amplified from all symptom-bearing tree samples and positive control DNAs, but not from DNA from the apparently healthy trees or seedlings. Restriction fragment length pattern analysis of PCR products with a range of endonucleases showed no difference between the Honduran and Costa Rican phytoplasma isolates. The distribution and symptom types observed in Costa Rica suggest that GLLD has recently arrived from Nicaragua and is spreading southeast. Reference: (1) L. Kenyon et al. Plant Pathol. 47:671, 1998.

Choroid coat extract and ciliary neurotrophic factor strongly promote neurite outgrowth in the embryonic chick retina.

Previous studies have shown that extracts from the target optic tectum stimulate neurite outgrowth from retinal explants. The present study indicates that the choroid coat is an even richer source of retinotrophic activity. We thus studied the effects of recombinant rat ciliary neurotrophic factor (CNTF) on primary cultures of dissociated chick ciliary ganglion neurons and retinal explants for a comparison with choroid coat extract from the E18 chick. For our assays, E9 ciliary neurons were incubated in collagen gels and retinal explants were cultured on collagen gels with the addition of the trophic factors and maintained for two or four days. Survival of ciliary neurons per area as well as maximal neurite length in retinal cultures were determined. Growth responses occurred in a dose-dependent manner both to CNTF and choroid extract. Immunofluorescence examination of cells and developing processes showed 200 kdal neurofilament positivity demonstrating that the cells studied were neurons with neurites. It is concluded that a trophic activity of the choroid as well as the recombinant CNTF stimulate retinal neuron survival and neurite extension. The results suggest that CNTF may have developmental functions in the establishment of the visual pathways.

Flowering plants: magic in bloom

Brief descriptions of the families of hallucinogenic plants which grow mainly in the tropical and subtropical regions of the New World. There is only occasional reference to the fact that these plants are found and used in specific Caribbean territories